Matsumoto writes that the whisper number for acquiring Big Switch is a paltry $100 million, less than half of the company's valuation as of its 2012 funding round. The loss in value can be traced to a couple of things: not being bought shortly after VMware paid $1.26 billion for start-up Nicira, developer of the NSX platform; and former ecosystem partners - like Juniper - and non-partners, like HP and Alcatel-Lucent, developing or acquiring their own controllers.

"Nobody wanted to be dependent on Big Switch" in case the start-up was acquired by a competitor or raised the price of its technology to unattractive levels, says Gartner analyst Joe Skorupa.

And we see a third and fourth reason Cisco might buy Big Switch. SDN customers like Fidelity and Goldman Sachs, even though Cisco is undoubtedly in those accounts already; and killing a competitor. One hundred million dollars is a pittance to a company with a $50 billion cash hoard stashed in bank accounts around the world. Shaving off .2% of that to eliminate a nuisance seems an undetectably small sacrifice.

It would also keep Big Switch from falling into the hands of a more formidable competitor.

"Why would they want a fourth controller?" asks Skorupa, of Cisco's reported interest in Big Switch products. "Unless they want to keep it from a competitor - buy the asset and bury it in a landfill."

More likely suitors for Big Switch might be data center and hypervisor titans without an SDN controller: Dell, Brocade and Microsoft, Skorupa speculates.

Microsoft could buy Big Switch to respond to VMware's NSX; and Brocade might find that its participation in and support for OpenDaylight amounts to very little differentiation and commercial success, Skorupa suggests.

Jim Duffy has been covering technology for over 28 years, 23 at Network World. He covers enterprise networking infrastructure, including routers and switches. He also writes The Cisco Connection blog and can be reached on Twitter @Jim_Duffy and at jduffy@nww.com.